This invention relates to magnetic head suspensions and in particular to the attachment of an air bearing slider to a magnetic head suspension.
Typically, a disk drive contains a number of magnetic disks attached to a common spindle for rotation. The surfaces of the magnetic disks have an associated head arm assembly which includes a head gimbal assembly (HGA). The head arm assemblies are generally attached to an actuator for positioning magnetic transducers formed with the HGAs with reference to data tracks on the magnetic disks. An HGA typically comprises a load beam, a flexible element or a flexure, and a slider. The flexure has one end attached to the load beam while the slider is joined to the other end of the flexure. The slider carries one or more transducers at it trailing edge, as is well known in the art. Transducer wires are connected to the transducers to conduct signals between the transducers and head circuitry.
To achieve shorter data seeking time, disk drives are designed not only with fast spinning disks, but also with rapidly moving head suspensions for accessing the data tracks registered on the storage disks. For these reasons, the slider must be securely attached to the flexure. Moreover, the constant motion of the slider and the frictional action of the slider results in an accumulation of electrostatic charge of sufficient magnitude which can be detrimental to the magnetic head. Accordingly, a well designed magnetic head suspension should incorporate an efficient electrostatic discharge (ESD) path for the slider in the gimbal assembly.
The HGA serves to dynamically adjust the orientation of the slider to conform to the disk surface while the disk is spinning. The topology of the disk surface, though highly polished, is not uniform if viewed at a microscopic scale. Moreover, the disk surfaces are not rotating about the common shaft at a perfectly perpendicular angle. A minute angular deviation would translate into varying disk-to-slider distances while the disk is spinning. For reliable data writing and reading, the slider thus has to faithfully follow the topology of the spinning disk.
Sliders are commonly attached to the flexure with adhesives that are resilient and are capable of buffering the thermal mismatches between the slider and the flexure. However, the use of adhesive to secure the slider to the flexure is undesirable because the manufacturing process is time-consuming and tedious. Applying an adhesive involves dispensing more than one adhesive component, for example, the epoxy base and the hardening agent. During production, the adhesive components are thoroughly mixed prior to application. After the adhesive is dispensed in a predetermined pattern on either the slider or the flexure, the slider is carefully aligned with the flexure for attachment. The amount of adhesive and the pattern need to be carefully controlled. Excessive adhesive may result in spillover causing undesirable problems. Deficiency in adhesive may compromise the overall adhesive effect. The adhesive is thereafter cured by exposing the epoxy pattern to ultraviolet (UV) light. As a further safeguard, the attached slider normally undergoes another elevated temperature curing process within the temperature range of between 100xc2x0 C.-200xc2x0 C.
The selected pattern on the flexure for UV light exposure has to be carefully designed. Normally, several openings are formed on the flexure as shown in FIG. 9. UV light is illuminated from the back side of the flexure through the openings. The gap between the slider and the flexure allows the UV light to disperse and permeate the adhesive. If the openings are too large, the adhesive force per areal unit is reduced. On the other hand, if the openings are too small, there may be insufficient UV light to pass through which may result in spotty areas of uncured adhesives. Thus, the slider may separate from the flexure during operation of the disk drive. Furthermore, outgassing from uncured adhesives are sources of contamination in the disk drive.
The number of manufacturing steps can be reduced with the use of single-component adhesives. In such cases, the processes of premixing the constituent components are avoided. However, the subsequent steps of UV curing light and high-heat annealing are still required. The elevated temperatures in the curing and annealing processes may be damaging to the read/write transducers disposed on the air bearing slider. Consequently, production yield may be undesirably reduced.
Even with the advent of automatic manufacturing processes in magnetic head suspension fabrication, the adhesives are still commonly dispensed manually with potential contamination. The harmful effect of constant UV light exposure to the operator is also of concern.
In addition to the tedious processes mentioned above, the use of adhesives is not very effective in regard to ESD dissipation. As mentioned before, electrostatic charge built up in the slider during constant movements needs to be effectively discharged. If the assembly is electrically isolated, the built-up electrostatic charge can affect data integrity and can even damage the magnetic head. With the conventional method, the discharge is realized via conducting charge through the adhesive with metallic particles. The high resistance value substantially impedes any efficient flow of electrostatic discharge. Therefore relying on the cured adhesives for ESD protection does not appear to be a viable solution.
It is an object of the invention to provide a magnetic head suspension assembly with a slider reliably and economically attached to the assembly.
It is another object of the invention to provide a magnetic head suspension assembly having an effective ESD path.
It is a further object of the invention to provide a magnetic head suspension having an air bearing slider attached to the suspension without annealing and curing processes, thereby realizing an improved production yield.
In accordance with this invention, a magnetic head suspension includes a load beam, a flexible member or flexure, and a slider, wherein a plurality of bonding pads are disposed on the flexure. Formed on the edge surfaces of the slider is another plurality of bonding pads. The bonding pads of the slider and the corresponding bonding pads on the flexure are attached to each other via bonding joints. In the preferred embodiment, the bonding joints are attached to the bonding pads through ultrasonic means. In the final head assembly, one of the bonding pads is electrically tied to the electrostatic discharge (ESD) path, and the other bonding pads are connected to electrical signal traces which are linked to the read and write transducers. Thus, the time-consuming steps of epoxy application can be avoided resulting in a more reliable and accurately oriented slider in the final magnetic head suspension assembly.